A well known problem in communication systems is intersymbol interference induced on a digital communication waveform by the dispersive properties of a transmission channel.
In most wireless communication systems, a transmitter will radiate its output signal in all directions. This radiated data can reflect off buildings, windows, and other surfaces. A receiver will therefore receive data from the transmitter which has traveled in a variety of routes. For example, an individual symbol of data may reach the receiver by traveling in a straight line, and may also reach it by reflecting from a building, and may further reach the receiver by first reflecting from a body of water, then off a different building. This will mean that the same symbol will travel from transmitter to receiver by three paths. This phenomena us referred to as multipath.
The result of this multipath effect is that each symbol is in effect smudged in time, and each symbol sent by the transmitter blurs into adjacent symbols. Therefore, the received waveform at any given time is dependent on some number of previous symbols. This is known as intersymbol interference. Furthermore, this multipath effect, as well as other effects, are what causes dispersion in the channel.
A class of equalizers, known as Maximum Likelihood Sequence Estimators (MLSE) has been developed to correct for this intersymbol interference. Many of this type of equalizer have incorporated what is known as the Viterbi Algorithm for use in determining the most likely sequence. This Algorithm is however, very computationally intensive, and requires a great deal of memory which must be integrated onto a VLSI chip designed to include an MLSE. Embodiments of the present invention provide improvements to an MLSE resulting in reduced memory requirements, simpler computational complexity, and improved accuracy. These improvements lead to reduced power consumption, smaller die size for the VLSI circuit.